With the vigorous development of the wireless communication technology, more and more users are using various mobile devices (e.g., intelligent mobile phones, tablet computers or the like) to transmit data for purposes of communication and multimedia audio & video (AV) transmission or the like. To ensure that mobile communication services of superior quality are provided for users, mobile communication operators obtain licensed bands by bidding for the licensed bands.
However, because of the growing number of users and the limited licensed band radio resources, it is often the case that a base station in a particular region (e.g., a user-intensive region such as a commercial zone, a traffic hub or the like) cannot provide sufficient radio resources for users in the region at the same time, and this results in the decrease of the transmission speed. For example, in order to serve a large number of UEs at the same time, the radio resource allocated by the base station to each UE will be limited. In this case, if the user wants to transmit a relatively large volume of data (e.g., upload films or pictures having a relatively large volume of data), then the limited licensed band radio resource usually cannot satisfy the transmission demand of the user, and thus the user will feel less satisfied with the mobile communication service quality.
To solve the problem of the limited licensed band radio resource, currently specialists and operators in the fourth generation long term evolution (4G LTE) mobile communication field have proposed use of unlicensed bands to assist in the signal transmission, i.e., the Licensed Assisted Access (LAA) technology. However, the conventional base station allocates the radio resources of the unlicensed bands to UEs individually and independently.
In detail, when a user needs to transmit uplink data, the base station can allocate a radio resource of an unlicensed band in response to the transmission demand of the user. For example, the base station may allocate part of radio resources of a specific subframe on a specific carrier to a UE so that the UE contends for the subframe through the listen before talk (LBT) procedure. That is, a clear channel assessment (CCA) is performed on the subframe to determine whether the carrier is available, and after it is determined that the carrier is available, a reservation signal is transmitted to ensure that the uplink data can be subsequently transmitted.
However, if the UE fails the contention in the current LAA mechanism, then the base station needs to reschedule to allocate a new radio resource of the unlicensed band to the UE until the UE has successfully contended for the radio resource and transmitted the uplink data. These repeated and ineffective scheduling operations will cause a serious delay in the uplink data transmission and an additional burden for the base station.
Moreover, to enable the radio resource of the unlicensed band to be used by the UEs that it serves, the base station may allocate a same subframe to several UEs so that the UEs content for the same subframe at the same time. However, for the current LAA mechanism, inter-blocking might occur between the UEs. In this case, even if each UE only uses part of the radio resource of the subframe, the radio resource of the subframe still cannot be allocated to different UEs for use. In other words, when a user has successfully contended for a subframe and transmitted a reservation signal, the reservation signal will be detected by other UEs and thus the other UEs fail the contention and cannot use the subframe. Accordingly, the conventional LAA mechanism still cannot make full use of the radio resources of the unlicensed band.
Accordingly, an urgent need exists in the art to provide an uplink transmission control mechanism which can make full use of the radio resources of the unlicensed band to meet the transmission demands of the users.